Centrifugal fan



July 29, 1941-,

E. F. ROETTGER CENTRIFUGAL FAN 2 Sheets-Sheet 2 Filed Jan. 13, 1940 INVENTOR ERv/N f-T R05 7765?,

. grinding ring 8.

Patented July 29, 1941 1 Combustion Engineering Company,

York, N. Y.

1110., New

Application January 13, 1940, Serial No. 313,393

4 Claims.

My invention relates to pumps and particularly to pneumatic pumps of the centrifugal type.

Centrifugal pumps or fans used to convey material in flotation in a fluid are subject to wear by impingement and erosion of the particles of material as they pass over the impellers or blades. I have found that when the material entering the intake of a suction fan is unequally distributed over the cross section of the intake in such away that a localized relative concentration occurs at one portion of the cross section, the-blades of the fan wear more at the portions where this concentration contacts them than at the remaining portions.

The object of this invention is to provide means at the inlet of the fan for distributing the material entering in flotation in a fluid more uniformly over the cross section of the inlet, thereby eliminating the localized excess wear on the fan blades.

How the foregoing, together with such other objects and advantages as may hereinafter appear or are incident to my invention are realized, is illustrated in preferred form in the accompanying drawings, wherein Fig. 1 shows a cross section of an exhauster fan on a pulverizer mill, the mill being shown half in elevation and half in section.

Fig. 2 is a horizontal sectional View through a fan blade taken on lines 2-2 of Fig. 1.

Fig. 3 is a longitudinal cross section through an inlet elbow for the fan embodying the present invention.

Fig. 4 is a transverse sectional view taken on line 4-4 of Fig. 3.

Fig. 5 is a view-on line 5-5 of Fig. 3 and shows damper-like deflectors located in the duct leading to the fan intake.

In Fig. 1, the numeral I indicates a pulverizing mill receiving raw material from a hopper 2. The mill bowl 4 is revolved by means of a motor 5 through shaft 6 and suitable gearing. The material delivered to the bowl is thrown centrifugally against a grinding ring 8, crushed under rollers 9 and spills over the top edge of the Thence it is carried by an air current flowing upward around the grinding ring through space I4 into a classifier. The coarse material travels downwardly back into the mill through the bottom of a conical separator I8 while the fine material passes upwardly in a current of air into a conduit 2| leading to a centrifugal suction fan 22. The mixture of pulverized material and air is then delivered by fan 22 through a conduit 23 to the place of use.

In the arrangement illustrated the mixture of ground material and air enters the fan inlet 24 throughan elbow 25. The material carried in flotation in the air through conduit 2| tends to continue its direction toward the outer radius of the elbow as shown approximately by the arrowheaded lines 26. The material when leaving the elbow and passing through the intake into interior of the fan passes across the blades 20 approximately as shown by the lines 26. The blades beingrotatable on an axis substantially coincident with the center of conduit and the fan intake, are exposed to the abrasion of the material on approximately the half'side thereof located nearest-the intake. The resultant wear is. indicated in Fig. 2 where the leftside of the blade has substantially its'original thickness but thins outto-the-right until the right side edge of the blade is almost worn through.

To overcome this difliculty I provide a novel means within the elbow 25 for distributing the material substantially uniformly over at least one half of the area of the intake 24 to the fan 22 so that the material passing into the fan reaches the left side of the fan blade as well as the right and in this way produce a uniform wear on the fan blades.

In Figs. 3 and 4 the inner wall surface at the outer radius of the elbow 25 is shown to be provided with transverse deflectors 21 which are shaped to extend inwardly and forwardly so that they tend to scoop up the material away from the outer Wall of the elbow and throw it upwardly back into the air stream. The result is that instead of having all of the material tend to concentrate at the outer portion of the elbow there is created a state of turbulence at this location which keeps the material in suspension and tends to deflect it back towards the inner portion of the elbow. The deflectors 21 are preferably scoop shaped as shown and may be cast inte grally with the elbow or may be removable sections fastened to the elbow as by bolts 28. A preferred shape for the deflector as seen transversely of the elbow is shown in Fig. 4.

To further assure against any tendency toward unequal distribution of the material as it is led to the elbow, I provide damper-like deflectors 29 as shown in Figs. 3 and 5. 'These deflectors 29 are made in right and left hand segments which are symmetrically placed with respect to the center line of the elbow and are so mounted on shafts 30 that they are balanced. The deflectors have their inner edges spaced and they are of such size as to leave substantial clearances between their outer edges and the conduit wall. They are also formed with holes so that even when they are fully closed there will be a fair distribution of material passing around and through the apertures and holes.

It should be understood that the invention is applicable also to straight ducts or those which have a shape other than an elbow and. where the material tends to collect in major portion to one side of the duct at the inlet of the fan.

What I claim is:

1. In combination with a centrifugal suction fan for transporting an abrasive material in a carrier fluid having rotor blades turning on an axis substantially coincident with the center of the fan intake and a conduit for delivering said mixture to the intake of the fan, wherein the material in the carrier fluid tends to become concentrated near one wall of said conduit and at one side of said rotor axis so as to cause uneven wear of said fan blades; deflecting members disposed transversely of the inner wall of said conduit adjacent the fan intake and extending inwardly and forwardly for directing the concentrated material toward the center of said fan intake.

2. In combination with a centrifugal suction fan for transporting an abrasive material in a carrier fluid having rotor blades turning on an axis substantially coincident with the center of the fan intake and a conduit for delivering said mixture to the intake of a fan, wherein the material in the carrier fluid tends to become concentrated near one wall of said conduit and at one side of the center of said fan intake so as to cause uneven wear of said fan blades; deflecting means disposed in said conduit at each side of the axis thereof and extending inwardly and forwardly with respect to the direction of flow of material so as to direct the latter toward the central portion of said conduit.

3. In combination with a centrifugal suction fan for transporting an abrasive material in a carrier fluid having rotor blades turning on an axis substantially coincident with the center of the fan intake and a conduit for delivering said mixture to the intake of a fan, wherein the material in the carrier fluid tends to become concentrated near one wall of said conduit and at one side of the center of said fan intake so as to cause uneven wear of said fan blades; adjustable deflecting means disposed in said conduit at each side of the axis thereof and extending inwardly and forwardly with respect to the direction of flow of material so as to direct the latter toward the central portion of saidv conduit; and shafts adjustably supporting said deflectors in said duct.

4. In combination with a centrifugal suction fan for transporting an abrasive material in a carrier fluid having rotor blades turning on an axis substantially coincident with the center of the fan intake and a conduit for delivering said mixture to the intake of a fan, wherein the material in the carrier fluid tends to become concentrated near one wall of said conduit and at one side of the center of said fan intake so as to cause uneven wear of said fan blades; deflecting means disposed in said conduit at each side of the axis thereof and extending inwardly and forwardly with respect to the direction of flow of material so as to direct the latter toward the central portion of said conduit, said deflectors occupying less than the full cross-sectional area of said conduit.

ERVIN F. ROETTGER. 

